Inactivation kinetics of Agaricus bisporus tyrosinase treated by ohmic heating: Influence of moderate electric field

The tyrosinase is a binuclear copper enzyme that catalyzes the oxidation of phenolics compounds to quinones in presence of molecular oxygen, which subsequently polymerized to dark brown pigments. To evaluate the effect of ohmic heating (OH) on the inactivation kinetics of Agaricus bisporus tyrosinase the independent variables were: electric field strength (25, 30, 35 V/cm), process time (0–15 min) and temperature (50–58 ± 1 °C). The conventional thermal treatment (CT) was used as a control. The results showed that the electric field decreased the time (D-value) required obtaining the same degree of tyrosinase inactivation at a target temperature compared to the CT. This indicates that the electric field acted synergistically with temperature to inactivate tyrosinase. The activation energy (E_a) calculated for the CT was 227.32 kJ mol⁻¹, while for the OH they were 146.52, 135.14 and 124.87 kJ mol⁻¹ for electric field strengths of 25, 30, and 35 V/cm respectively. In this study, a direct relationship between the E_a and the electric field is shown. Results demonstrated that the OH is an effective technology to inactivate tyrosinase, allowing it to be used in thermal process such as pasteurization or blanching.